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ksh93(1CDE)
CDE
NAME
ksh93 - implementation of Korn shell libraries called by dtksh
SYNOPSIS
Not applicable
DESCRIPTION
The ksh93 environment is the implementation of the Korn shell libraries
called by the dtksh command language interpreter. It cannot be invoked from
the command line. Refer to dtksh(1) for more information.
Definitions
A metacharacter is one of the following characters:
; & ( ) | < > newline space tab
A blank is a tab or a space. An identifier is a sequence of letters,
digits, or underscores starting with a letter or underscore. Identifiers
are used as components of variable names. A vname is a sequence of one or
more identifiers separated by a . and optionally preceded by a .. Vnames
are used as function and variable names. A word is a sequence of characters
excluding non-quoted metacharacters.
A command is a sequence of characters in the syntax of the shell language.
The shell reads each command and carries out the desired action either
directly or by invoking separate utilities. A built-in command is a
command that is carried out by the shell itself without creating a separate
process. Some commands are built-in purely for convenience and are not
documented here. Built-ins that cause side effects in the shell environment
and built-ins that are found before performing a path search (see Execution
below) are documented here. For historical reasons, some of these built-ins
behave differently than other built-ins and are called special built-ins.
Commands
A simple-command is a list of variable assignments (see Variable
Assignments below) or a sequence of blank separated words which may be
preceded by a list of variable assignments (see Environment below). The
first word specifies the name of the command to be executed. Except as
specified below, the remaining words are passed as arguments to the invoked
command. The command name is passed as argument 0 (see exec(2)). The value
of a simple-command is its exit status; 0-255 if it terminates normally;
256+signum if it terminates abnormally (the name of the signal
corresponding to the exit status can be obtained via the "-l $?" option of
the kill built-in utility).
An arithmetic command begins with a ((, and consists of an arithmetic
expression formed by all the characters until a matching )). (See
Arithmetic Evaluation below.) The exit status of an arithmetic command is 0
when the arithmetic expression evaluates to a non-zero value and is 1 when
the arithmetic expression evaluates to 0.
A pipeline is a sequence of one or more commands separated by |. The
standard output of each command but the last is connected by a pipe(2) to
the standard input of the next command. Each command, except possibly the
last, is run as a separate process; the shell waits for the last command to
terminate. The exit status of a pipeline is the exit status of the last
command. Each pipeline can be preceded by the reserved word ! which negates
the exit status of the pipeline.
A list is a sequence of one or more pipelines separated by ;, &, |&, &&, or
||, and optionally terminated by ;, &, or |&. Of these five symbols, ;, &,
and |& have equal precedence, which is lower than that of && and ||. The
symbols && and || also have equal precedence. A semicolon (;) causes
sequential execution of the preceding pipeline; an ampersand (&) causes
asynchronous execution of the preceding pipeline (i.e., the shell does not
wait for that pipeline to finish). The symbol |& causes asynchronous
execution of the preceding pipeline with a two-way pipe established to the
parent shell; the standard input and output of the spawned pipeline can be
written to and read from by the parent shell by applying the redirection
operators <& and >& with arg p to commands and by using -p option of the
built-in commands read and print described later. The symbol && (||) causes
the list following it to be executed only if the preceding pipeline returns
a zero (non-zero) value. An arbitrary number of newlines may appear in a
list instead of a semicolon, to delimit a command.
A command is either a simple-command or one of the following. Unless
otherwise stated, the value returned by a command is that of the last
simple-command executed in the command.
for vname [ in word ... ] ;do list ;done
Each time a for command is executed, name is set to the next word taken
from the in word list. If in " word" ... is omitted, then the for
command executes the do list once for each positional parameter that is
set (see Parameter Expansion below). Execution ends when there are no
more words in the list.
for (( [expr1] ; [expr2] ; [expr3] )) ;do list ;done
The arithmetic expression expr1 is evaluated first. (See Arithmetic
Evaluation below.) The arithmetic expression expr2 is repeatedly
evaluated until it evalues to zero and when non-zero, list is executed
and the arithmetic expression expr3 evaluated. If any expression is
omitted, then it behaves as if it evaluated to 1.
select vname [ in word ... ] ;do list ;done
A select command prints on standard error (file descriptor 2) the set
of words, each preceded by a number. If in " word" ... is omitted,
then the positional parameters are used instead (see Parameter
Expansion below). The PS3 prompt is printed and a line is read from the
standard input. If this line consists of the number of one of the
listed words, then the value of the variable vname is set to the word
corresponding to this number. If this line is empty the selection list
is printed again. Otherwise the value of the variable vname is set to
null. The contents of the line read from standard input is saved in the
variable REPLY. The list is executed for each selection until a break
or end-of-file is encountered. If the REPLY variable is set to null by
the execution of list, then the selection list is printed before
displaying the PS3 prompt for the next selection.
case word in [ [ ( ]pattern [ | pattern ] ... ) list ;; ] ... esac
A case command executes the list associated with the first pattern that
matches word. The form of the patterns is the same as that used for
file-name generation (see File Name Generation below). The ;; operator
causes execution of case to terminate. If ;& is used in place of ;; the
next subsequent list, if any, is executed.
if list ;then list [ elif list ;then list ] ... [ ;else list ] ;fi
The list following if is executed and, if it returns a zero exit
status, the list following the first then is executed. Otherwise, the
list following elif is executed and, if its value is zero, the list
following the next then is executed. Failing that, the else list is
executed. If the if list has non-zero exit status and there is no else
list, then the if command returns a zero exit status.
while list ;do list ;done
until list ;do list ;done
A while command repeatedly executes the while list and, if the exit
status of the last command in the list is zero, executes the do list;
otherwise the loop terminates. If no commands in the do list are
executed, then the while command returns a zero exit status; until may
be used in place of while to negate the loop termination test.
(list)
Execute list in a separate environment. Note, that if two adjacent
open parentheses are needed for nesting, a space must be inserted to
avoid evaluation as an arithmetic command as described above.
{ list;}
list is simply executed. Note that unlike the metacharacters ( and ), {
and } are reserved word and must occur at the beginning of a line or
after a ; in order to be recognized.
[[ expression ]]
Evaluates expression and returns a zero exit status when expression is
true. See Conditional Expressions below, for a description of
expression.
function varname { list ;}
varname () { list ;}
Define a function which is referenced by varname. A function whose
varname contains a . is called a discipline function and the portion of
the varname preceding the last . must refer to an existing variable.
The body of the function is the list of commands between { and }. A
function defined with the function varname syntax can also be used as
an argument to the . special built-in command to get the equivalent
behavior as if the varname() syntax were used to define it. (See
Functions below.)
time [ pipeline ]
If pipeline is omitted the user and system time for the current shell
and completed child processes is printed on standard error. Otherwise,
pipeline is executed and the elapsed time as well as the user and
system time are printed on standard error. The following reserved words
are only recognized as such when they are the first word of a command
and are not quoted:
if then else elif fi case esac for while until do done { }
function select time [[ ]] !
Variable Assignments
One or more variable assignments can start a simple command or can be an
arguments to the typeset, export, or readonly special built-in commands.
The syntax for an assignment is of the form:
varname=word
varname[word]=word
No space is permitted between varname and the = or between = and word.
varname=(assign_list)
No space is permitted between varname and the =. An assign_list can be
one of the following:
word ...
Indexed array assignment.
[word]=word ...
Associative array assignment.
assignment ...
Nested variable assignment.
typeset [options] assignment ...
Nested variable assignment. Multiple assignments can be specified
by separating each of them with a ;.
Comments
A word beginning with # causes that word and all the following characters
up to a newline to be ignored.
Aliasing
The first word of each command is replaced by the text of an alias if an
alias for this word has been defined. An alias name consists of any number
of characters excluding metacharacters, quoting characters, file expansion
characters, parameter expansion and command substitution characters, and =.
The replacement string can contain any valid shell script including the
metacharacters listed above. The first word of each command in the replaced
text, other than any that are in the process of being replaced, will be
tested for aliases. If the last character of the alias value is a blank
then the word following the alias will also be checked for alias
substitution. Aliases can be used to redefine built-in commands but cannot
be used to redefine the reserved words listed above. Aliases can be created
and listed with the alias command and can be removed with the unalias
command.
Aliasing is performed when scripts are read, not while they are executed.
Therefore, for an alias to take effect the alias definition command has to
be executed before the command which references the alias is read.
The following exported aliases are compiled into the shell but can be unset
or redefined:
"autoload='typeset -fu'"
"command='command '"
"fc=hist"
"float='typeset -E'"
"functions='typeset -f'"
"hash='alias -t --'"
"history='hist -l'"
"integer='typeset -i'"
"nameref='typeset -n'"
"nohup='nohup '"
"r='hist -s'"
"redirect='command exec'"
"stop='kill -s STOP'"
"times='{ {time;} 2>&1;}'"
"type='whence -v'"
Tilde Substitution
After alias substitution is performed, each word is checked to see if it
begins with an unquoted ~. For tilde substitution, word also refers to the
word portion of parameter expansion (see Parameter Expansion below.) If it
does, then the word up to a / is checked to see if it matches a user name
in the password database (often the /etc/passwd file). If a match is found,
the ~ and the matched login name are replaced by the login directory of the
matched user. If no match is found, the original text is left unchanged. A
~ by itself, or in front of a /, is replaced by $HOME. A ~ followed by a +
or - is replaced by the value of $PWD and $OLDPWD respectively.
In addition, when expanding a variable assignment tilde substitution is
attempted when the value of the assignment begins with a ~, and when a ~
appears after a :. The : also terminates a ~ login name.
Command Substitution
The standard output from a command enclosed in parentheses preceded by a
dollar sign ($()) or a pair of grave accents (` `) may be used as part or
all of a word; trailing newlines are removed. In the second (obsolete)
form, the string between the quotes is processed for special quoting
characters before the command is executed (see Quoting below). The command
substitution $(cat file) can be replaced by the equivalent but faster
$(<file).
Arithmetic Substitution
An arithmetic expression enclosed in double parentheses preceded by a
dollar sign ($(())) is replaced by the value of the arithmetic expression
within the double parentheses.
Process Substitution
This feature is only available on versions of the UNIX operating system
that support the /dev/fd directory for naming open files. Each command
argument of the form <(list) or >(list) will run process list
asynchronously connected to some file in /dev/fd. The name of this file
will become the argument to the command. If the form with > is selected
then writing on this file will provide input for list. If < is used, then
the file passed as an argument will contain the output of the list process.
For example,
paste <(cut -f1 file1) <(cut -f3 file2) | tee >(process1) >(process2)
cuts fields 1 and 3 from the files file1 and file2 respectively, pastes the
results together, and sends it to the processes process1 and process2, as
well as putting it onto the standard output. Note that the file, which is
passed as an argument to the command, is a UNIX pipe(2) so programs that
expect to lseek(2) on the file will not work.
Parameter Expansion
A parameter is an variable, one or more digits, or any of the characters *,
@, #, ?, -, $, and !\^. A variable is denoted by a vname. To create a
variable whose vname contains a ., a variable whose vname consists of
everything before the last . must already exist. A variable has a value and
zero or more attributes. Variables can be assigned values and attributes
by using the typeset special built-in command. The attributes supported by
the shell are described later with the typeset special built-in command.
Exported variables pass values and attributes to the environment.
The shell supports both indexed and associative arrays. An element of an
array variable is referenced by a subscript. A subscript for an indexed
array is denoted by an arithmetic expression (see Arithmetic Evaluation
below) between a [ and a ]. To assign values to an indexed array, use set
-A vname value ... . The value of all subscripts must be in the range of 0
through 4095. Indexed arrays need not be declared. Any reference to a
variable with a valid subscript is legal and an array will be created if
necessary.
An associative array is created with the -A option to typeset. A subscript
for an associative array is denoted by a string enclosed between [ and ].
Referencing any array without a subscript is equivalent to referencing the
array with subscript 0.
The value of a variable may be assigned by writing:
vname = value
[
vname = value
] ...
or
vname [ subscript ]= value
[
vname [ subscript ]= value
] ...
Note that no space is allowed before or after the =.
A nameref is a variable that is a reference to another variable. A nameref
is created with the -n attribute of typeset. The value of the variable at
the time of the typeset command becomes the variable that will be
referenced whenever the nameref variable is used. The name of a nameref
variable cannot contain a .. When a variable or function name contains a .,
and the portion of the name up to the first . matches the name of a
nameref, the variable referred to is obtained by replacing the nameref
portion with the name of the variable referenced by the nameref. A nameref
provides a convenient way to refer to the variable inside a function whose
name is passed as an argument to a function. For example, if the name of a
variable is passed as the first argument to a function, the command
typeset -n var=$1
inside the function causes references and assignments to var to be
references and assignments to the variable whose name has been passed to
the function.
If either of the floating point attributes, -E, or -F, or the integer
attribute, -i, is set for vname, then the value is subject to arithmetic
evaluation as described below.
Positional parameters, parameters denoted by a number, may be assigned
values with the set special built-in command. Parameter $0 is set from
argument zero when the shell is invoked.
The character $ is used to introduce substitutable parameters.
${parameter}
The shell reads all the characters from ${ to the matching } as part of
the same word even if it contains braces or metacharacters. The value,
if any, of the parameter is substituted. The braces are required when
parameter is followed by a letter, digit, or underscore that is not to
be interpreted as part of its name, when the variable name contains a
., or when a variable is subscripted. If parameter is one or more
digits then it is a positional parameter. A positional parameter of
more than one digit must be enclosed in braces. If parameter is * or @,
then all the positional parameters, starting with $1, are substituted
(separated by a field separator character). If an array vname with
subscript * or @ is used, then the value for each of the elements is
substituted (separated by a field separator character).
${#parameter}
If parameter is * or @, the number of positional parameters is
substituted. Otherwise, the length of the value of the parameter is
substituted.
${#vname[*]}
The number of elements in the array vname is substituted.
${!vname}
Expands to the name of the variable referred to by vname. This will be
vname except when vname is a name reference.
${!vname[subscript]}
Expands to name of the subscript unless subscript is *, or @. When
subscript is *, the list of array subscripts for vname is generated.
For a variable that is not an array, the value is 0 if the variable is
set. Otherwise it is null. When subscript is @, same as above, except
that when used in double quotes, each array subscript yields a separate
argument.
${!prefix*}
Expands to the names of the variables whose names begin with prefix.
${parameter:-word}
If parameter is set and is non-null then substitute its value;
otherwise substitute word.
${parameter:=word}
If parameter is not set or is null then set it to word; the value of
the parameter is then substituted. Positional parameters may not be
assigned to in this way.
${parameter:?word}
If parameter is set and is non-null then substitute its value;
otherwise, print word and exit from the shell. If word is omitted then
a standard message is printed.
${parameter:+word}
If parameter is set and is non-null then substitute word; otherwise
substitute nothing.
${parameter:offset:length}
${parameter:offset}
Expands to the portion of the value of parameter starting at the
character determined by expanding offset as an arithmetic expression
and consisting of the number of characters determined by the arithmetic
expression defined by length. In the second form, the remainder of the
value is used. If parameter is * or @, or is an array name indexed by
* or @, then offset and length refer to the array index and number of
elements respectively.
${parameter#pattern}
${parameter##pattern}
If the shell pattern matches the beginning of the value of parameter,
then the value of this expansion is the value of the parameter with the
matched portion deleted; otherwise the value of this parameter is
substituted. In the first form the smallest matching pattern is deleted
and in the second form the largest matching pattern is deleted. When
parameter is @, *, or an array variable with subscript @, or *, the
substring operation is applied to each element in turn.
${parameter%pattern}
${parameter%%pattern}
If the shell pattern matches the end of the value of parameter, then
the value of this expansion is the value of the parameter with the
matched part deleted; otherwise substitute the value of parameter. In
the first form the smallest matching pattern is deleted and in the
second form the largest matching pattern is deleted. When parameter is
@, *, or an array variable with subscript @, or *, the substring
operation is applied to each element in turn.
${parameter/pattern/string}
${parameter//pattern/string}
Expands parameter and replaces pattern with the given string. In the
first form, only the first occurrence of pattern is replaced. In the
second form, each match for pattern is replaced by the given string.
When string is null, the pattern will be deleted and the / in front of
string may be omitted. When parameter is @, *, or an array variable
with subscript @, or *, the substitution operation is applied to each
element in turn.
In the above, word is not evaluated unless it is to be used as the
substituted string, so that, in the following example, pwd is executed only
if d is not set or is null:
print ${d:-$(pwd)}
If the colon ( : ) is omitted from the above expressions, then the shell
only checks whether parameter is set or not.
The following parameters are automatically set by the shell:
# The number of positional parameters in decimal.
- Options supplied to the shell on invocation or by the set command.
? The decimal value returned by the last executed command.
$ The process number of this shell.
_ Initially, the value of _ is an absolute pathname of the shell or
script being executed as passed in the environment. Subsequently it is
assigned the last argument of the previous command. This parameter is
not set for commands which are asynchronous. This parameter is also
used to hold the name of the matching MAIL file when checking for mail.
! The process number of the last background command invoked.
.sh.edchar
This variable contains the value of the keyboard character (or sequence
of characters if the first character is an ESC, ascii 033) that has
been entered when processing a KEYBD trap. If the value is changed as
part of the trap action, then the new value replaces the key (or key
sequence) that caused the trap.
.sh.edcol
The character position of the cursor at the time of the most recent
KEYBD trap.
.sh.edmode
The value is set to ESC when processing a KEYBD trap while in vi insert
mode. (See Vi Editing Mode below.) Otherwise, .sh.edmode is null when
processing a KEYBD trap.
.sh.edtext
The characters in the input buffer at the time of the most recent KEYBD
trap. The value is null when not processing a KEYBD trap.
.sh.name
Set to the name of the variable at the time of a set or get discipline
is invoked.
.sh.subscript
Set to the name subscript of the variable at the time of a set or get
discipline is invoked.
.sh.value
Set to the value of the variable at the time of a set discipline.
.sh.version
Set to a value that identifies the version of this shell.
LINENO
The line number of the current line within the script or function being
executed.
OLDPWD
The previous working directory set by the cd command.
OPTARG
The value of the last option argument processed by the getopts built-in
command.
OPTIND
The index of the last option argument processed by the getopts built-in
command.
PPID
The process number of the parent of the shell.
PWD The present working directory set by the cd command.
RANDOM
Each time this variable is referenced, a random integer, uniformly
distributed between 0 and 32767, is generated. The sequence of random
numbers can be initialized by assigning a numeric value to RANDOM.
REPLY
This variable is set by the select statement and by the read built-in
command when no arguments are supplied.
SECONDS
Each time this variable is referenced, the number of seconds since
shell invocation is returned. If this variable is assigned a value,
then the value returned upon reference will be the value that was
assigned plus the number of seconds since the assignment.
The following variables are used by the shell:
CDPATH
the search path for the cd command.
COLUMNS
If this variable is set, the value is used to define the width of the
edit window for the shell edit modes and for printing select lists.
EDITOR
If the value of this variable ends in emacs, gmacs, or vi and the
VISUAL
variable is not set, then the corresponding option (see Special Command
set below) will be turned on.
ENV If this variable is set, then parameter expansion, command
substitution, and arithmetic substitution, are performed on the value
to generate the pathname of the script that will be executed when the
shell is invoked. (See Invocation below.) This file is typically used
for alias and function definitions.
FCEDIT
Obsolete name for the default editor name for the hist command. FCEDIT
is not used when HISTEDIT is set.
FIGNORE
A pattern that defines the set of filenames that will be ignored when
performing filename matching.
FPATH
The search path for function definitions. This path is searched when a
function with the -u attribute is referenced and when a command is not
found. If an executable file is found, then it is read and executed in
the current environment.
IFS Internal field separators, normally space, tab, and newline that are
used to separate the results of command substitution or parameter
expansion and to separate fields with the built-in command read. The
first character of the IFS variable is used to separate arguments for
the "$*" substitution. (See Quoting below.) Each single occurrence of
an IFS character in the string to be split, except space, tab, and
newline, separates a field. One or more space, tab, or newline
characters separate a field.
HISTEDIT
Name for the default editor name for the hist command.
HISTFILE
If this variable is set when the shell is invoked, then the value is
the pathname of the file that will be used to store the command
history. (See Command Re-entry below.)
HISTSIZE
If this variable is set when the shell is invoked, then the number of
previously entered commands that are accessible by this shell will be
greater than or equal to this number. The default is 128.
HOME
The default argument (home directory) for the cd command.
LINES
If this variable is set, the value is used to determine the column
length for printing select lists. Select lists will print vertically
until about two-thirds of LINES lines are filled.
MAIL
If this variable is set to the name of a mail file and the MAILPATH
variable is not set, then the shell informs the user of arrival of mail
in the specified file.
MAILCHECK
This variable specifies how often (in seconds) the shell will check for
changes in the modification time of any of the files specified by the
MAILPATH or MAIL variables. The default value is 600 seconds. When the
time has elapsed the shell will check before issuing the next prompt.
MAILPATH
A colon ( : ) separated list of file names. If this variable is set
then the shell informs the user of any modifications to the specified
files that have occurred within the last MAILCHECK seconds. Each file
name can be followed by a ? and a message that will be printed. The
message will undergo parameter expansion, command substitution, and
arithmetic substitution with the variable $_ defined as the name of the
file that has changed. The default message is you have mail in $_.
PATH
The search path for commands (see Execution below). The user may not
change PATH if executing under rksh (except in .profile).
PS1 The value of this variable is expanded for parameter expansion, command
substitution, and arithmetic substitution to define the primary prompt
string which by default is ""$ "". The character ! in the primary
prompt string is replaced by the command number (see Command Re-entry
below). Two successive occurrences of ! will produce a single ! when
the prompt string is printed.
PS2 Secondary prompt string, by default "">"
PS3 Selection prompt string used within a select loop, by default ""#?"
PS4 The value of this variable is expanded for parameter evaluation,
command substitution, and arithmetic substitution and precedes each
line of an execution trace. If omitted, the execution trace prompt is
""+".
SHELL
The pathname of the shell is kept in the environment. At invocation, if
the basename of this variable is rsh, rksh, or krsh, then the shell
becomes restricted.
TMOUT
If set to a value greater than zero, the read built-in command
terminates after TMOUT seconds when input is from a terminal.
Otherwise, the shell will terminate if a line is not entered within the
prescribed number of seconds while reading from a terminal. (Note that
the shell can be compiled with a maximum bound for this value which
cannot be exceeded.)
VISUAL
If the value of this variable ends in emacs, gmacs, or vi then the
corresponding option (see Special Command set below) will be turned on.
The shell gives default values to PATH, PS1, PS2, PS3, PS4, MAILCHECK,
HISTEDIT, TMOUT and IFS, while HOME, SHELL, ENV, and MAIL are not set at
all by the shell (although HOME is set by login(1)). On some systems MAIL
and SHELL are also set by login(1).
Field Splitting
After parameter expansion and command substitution, the results of
substitutions are scanned for the field separator characters (those found
in IFS) and split into distinct fields where such characters are found.
Explicit null fields (" " or ' ') are retained. Implicit null fields (those
resulting from parameters that have no values or command substitutions with
no output) are removed.
File Name Generation
Following splitting, each field is scanned for the characters *, ?, (, and
[ unless the -f option has been set. If one of these characters appears
then the word is regarded as a pattern. Each file name component that
contains any pattern character is replaced with a lexicographically sorted
set of names that matches the pattern from that directory. If no file name
is found that matches the pattern, then that component of the filename is
left unchanged. If FIGNORE is set, then each file name component that
matches the pattern defined by the value of FIGNORE is ignored when
generating the matching filenames. The names . and .. are also ignored. If
FIGNORE is not set, the character . at the start of each file name
component will be ignored unless the first character of the pattern
corresponding to this component is the character . itself. Note, that for
other uses of pattern matching the / and . are not treated specially.
* Matches any string, including the null string.
? Matches any single character.
[...]
Matches any one of the enclosed characters. A pair of characters
separated by - matches any character lexically between the pair,
inclusive. If the first character following the opening [ is a ! then
any character not enclosed is matched. A - can be included in the
character set by putting it as the first or last character.
Within [ and ] character classes can be specified with the syntax
[:class:] where class is one of the following:
alnum alpha cntrl digit graph lower print punct
space upper xdigit
A pattern-list is a list of one or more patterns separated from each other
with a |. Composite patterns can be formed with one or more of the
following:
?(pattern-list)
Optionally matches any one of the given patterns.
*(pattern-list)
Matches zero or more occurrences of the given patterns.
+(pattern-list)
Matches one or more occurrences of the given patterns.
@(pattern-list)
Matches exactly one of the given patterns.
!(pattern-list)
Matches anything except one of the given patterns.
Quoting
Each of the metacharacters listed earlier (see Definitions above) has a
special meaning to the shell and causes termination of a word unless
quoted. A character may be quoted (i.e., made to stand for itself) by
preceding it with a \. The pair \newline is removed. All characters
enclosed between a pair of single quote marks (' ') that is not preceded
by a $ are quoted. A single quote cannot appear within the single quotes. A
single quoted string preceded an unquoted $ is processed as an ANSI-C
string except that \0 within the string causes the remainder of the string
to be ignored and \E is equivalent to the escape character (ascii 033).
Inside double quote marks (" "), parameter and command substitution occur
and \ quotes the characters \, `, ", and $. The meaning of "$*" and "$@" is
identical when not quoted or when used as a variable assignment value or as
a file name. However, when used as a command argument, "$*" is equivalent
to "$1d$2d...", where d is the first character of the IFS variable, whereas
"$@" is equivalent to "$1" "$2" .... Inside grave quote marks (` `), \
quotes the characters \, `, and $. If the grave quotes occur within double
quotes then \ also quotes the character ".
The special meaning of reserved words or aliases can be removed by quoting
any character of the reserved word. The recognition of function names or
built-in command names listed below cannot be altered by quoting them.
Arithmetic Evaluation
The shell performs arithmetic evaluation for arithmetic substitution, to
evaluate an arithmetic command, to evaluate an indexed array subscript, and
to evaluate arguments to the built-in commands shift and let. Evaluations
are performed using double precision floating point arithmetic. Floating
point constants follow the ANSI-C programming language conventions. Integer
constants are of the form [base#]n where base is a decimal number between
two and sixty-four representing the arithmetic base and n is a number in
that base. The digits above 9 are represented by the lower case
characters, the upper case characters, @, and _ respectively. For bases
less than 36, upper and lower case character can be used interchangeably.
If base is omitted then base 10 is used.
An arithmetic expression uses the same syntax, precedence, and
associativity of expression as the C language. All the C language operators
that apply to floating point quantities can be used. In addition, when the
value of an arithmetic variable or sub-expression can be represented as a
long integer, all C language integer arithmetic operations can be
performed. Variables can be referenced by name within an arithmetic
expression without using the parameter expansion syntax. When a variable is
referenced, its value is evaluated as an arithmetic expression. The
following math library functions can be used with an arithmetic expression:
abs acos asin atan cos cosh exp int log sin sinh sqrt tan tanh
An internal representation of a variable as a double precision floating
point can be specified with the -E [n] or -F [n] option of the typeset
special built-in command. The -E option causes the expansion of the value
to be represented using scientific notation when it is expanded. The
optional option argument n defines the number of significant figures. The
-F option causes the expansion to be represented as a floating decimal
number when it is expanded. The optional option argument n defines the
number of places after the decimal point in this case.
An internal integer representation of a variable can be specified with the
-i [n] option of the typeset special built-in command. The optional option
argument n specifies an arithmetic base to be used when expanding the
variable. If you do not specify an arithmetic base, the first assignment to
the variable determines the arithmetic base.
Arithmetic evaluation is performed on the value of each assignment to a
variable with the -E, -F, or -i attribute. Assigning a floating point
number to a variable whose type is an integer causes the fractional part to
be truncated.
Prompting
When used interactively, the shell prompts with the value of PS1 after
expanding it for parameter expansion, command substitution, and arithmetic
substitution, before reading a command. In addition, each single ! in the
prompt is replaced by the command number. A !! is required to place ! in
the prompt. If at any time a newline is typed and further input is needed
to complete a command, then the secondary prompt (i.e., the value of PS2)
is issued.
Conditional Expressions
A conditional expression is used with the [[ compound command to test
attributes of files and to compare strings. Field splitting and file name
generation are not performed on the words between [[ and ]]. Each
expression can be constructed from one or more of the following unary or
binary expressions:
string
True, if string is not null.
-a file
Same is -e below. This is obsolete.
-b file
True, if file exists and is a block special file.
-c file
True, if file exists and is a character special file.
-d file
True, if file exists and is a directory.
-e file
True, if file exists.
-f file
True, if file exists and is an ordinary file.
-g file
True, if file exists and is has its setgid bit set.
-k file
True, if file exists and is has its sticky bit set.
-n string
True, if length of string is non-zero.
-o option
True, if option named option is on.
-p file
True, if file exists and is a fifo special file or a pipe.
-r file
True, if file exists and is readable by current process.
-s file
True, if file exists and has size greater than zero.
-t fildes
True, if file descriptor number fildes is open and associated with a
terminal device.
-u file
True, if file exists and is has its setuid bit set.
-w file
True, if file exists and is writable by current process.
-x file
True, if file exists and is executable by current process. If file
exists and is a directory, then true if the current process has
permission to search in the directory.
-z string
True, if length of string is zero.
-L file
True, if file exists and is a symbolic link.
-O file
True, if file exists and is owned by the effective user id of this
process.
-G file
True, if file exists and its group matches the effective group id of
this process.
-S file
True, if file exists and is a socket.
file1 -nt file2
True, if file1 exists and is newer than file2.
file1 -ot file2
True, if file1 exists and is older than file2.
file1 -ef file2
True, if file1 and file2 exist and refer to the same file.
string == pattern
True, if string matches pattern. Any part of pattern can be quoted to
cause it to be matched as a string.
string = pattern
Same as == above, but is obsolete.
string != pattern
True, if string does not match pattern.
string1 < string2
True, if string1 comes before string2 based on ASCII value of their
characters.
string1 > string2
True, if string1 comes after string2 based on ASCII value of their
characters.
The following obsolete arithmetic comparisons are also permitted:
exp1 -eq exp2
True, if exp1 is equal to exp2.
exp1 -ne exp2
True, if exp1 is not equal to exp2.
exp1 -lt exp2
True, if exp1 is less than exp2.
exp1 -gt exp2
True, if exp1 is greater than exp2.
exp1 -le exp2
True, if exp1 is less than or equal to exp2.
exp1 -ge exp2
True, if exp1 is greater than or equal to exp2.
In each of the above expressions, if file is of the form /dev/fd/n, where n
is an integer, then the test is applied to the open file whose descriptor
number is n.
A compound expression can be constructed from these primitives by using any
of the following, listed in decreasing order of precedence.
(expression)
True, if expression is true. Used to group expressions.
! expression
True if expression is false.
expression1 && expression2
True, if expression1 and expression2 are both true.
expression1 || expression2
True, if either expression1 or expression2 is true.
Input/Output
Before a command is executed, its input and output may be redirected using
a special notation interpreted by the shell. The following may appear
anywhere in a simple-command or may precede or follow a command and are not
passed on to the invoked command. Command substitution, parameter
expansion, and arithmetic substitution occur before word or digit is used
except as noted below. File name generation occurs only if the shell is
interactive and the pattern matches a single file, Field splitting is not
performed.
< word
Use file word as standard input (file descriptor 0).
> word
Use file word as standard output (file descriptor 1). If the file does
not exist then it is created. If the file exists, and the noclobber
option is on, this causes an error; otherwise, it is truncated to zero
length.
>| word
Sames as >, except that it overrides the noclobber option.
>> word
Use file word as standard output. If the file exists then output is
appended to it (by first seeking to the end-of-file); otherwise, the
file is created.
<> word
Open file word for reading and writing as standard input.
<<[-]word
The shell input is read up to a line that is the same as word after any
quoting has been removed remove, or to an end-of-file. No parameter
substitution, command substitution, arithmetic substitution or file
name generation is performed on word. The resulting document, called a
here-document, becomes the standard input. If any character of word is
quoted, then no interpretation is placed upon the characters of the
document; otherwise, parameter expansion, command substitution, and
arithmetic substitution occur, \newline is ignored, and \ must be used
to quote the characters \, $, `. If - is appended to <<, then all
leading tabs are stripped from word and from the document.
<& digit
The standard input is duplicated from file descriptor digit (see
dup(2)). Similarly for the standard output using >&digit.
<&- The standard input is closed. Similarly for the standard output using
>&-.
<&p The input from the co-process is moved to standard input.
>&p The output to the co-process is moved to standard output.
If one of the above is preceded by a digit, then the file descriptor number
referred to is that specified by the digit (instead of the default 0 or 1).
For example:
...2>&1
means file descriptor 2 is to be opened for writing as a duplicate of file
descriptor 1.
The order in which redirections are specified is significant. The shell
evaluates each redirection in terms of the file descriptor association at
the time of evaluation. For example:
...1>fname 2>&1
first associates file descriptor 1 with file fname. It then associates
file descriptor 2 with the file associated with file descriptor 1 (i.e.
fname). If the order of redirections were reversed, file descriptor 2 would
be associated with the terminal (assuming file descriptor 1 had been) and
then file descriptor 1 would be associated with file fname.
If a command is followed by & and job control is not active, then the
default standard input for the command is the empty file /dev/null.
Otherwise, the environment for the execution of a command contains the file
descriptors of the invoking shell as modified by input/output
specifications.
Environment
The environment (see environ(2)) is a list of name-value pairs that is
passed to an executed program in the same way as a normal argument list.
The names must be identifiers and the values are character strings. The
shell interacts with the environment in several ways. On invocation, the
shell scans the environment and creates a variable for each name found,
giving it the corresponding value and attributes and marking it export.
Executed commands inherit the environment. If the user modifies the values
of these variables or creates new ones, using the export or typeset -x
commands they become part of the environment. The environment seen by any
executed command is thus composed of any name-value pairs originally
inherited by the shell, whose values may be modified by the current shell,
plus any additions which must be noted in export or typeset -x commands.
The environment for any simple-command or function may be augmented by
prefixing it with one or more variable assignments. A variable assignment
argument is a word of the form identifier=value. Thus:
TERM=450 cmd args and
(export TERM; TERM=450; cmd args)
are equivalent (as far as the above execution of cmd is concerned except
for special built-in commands listed below--those that are preceded with an
asterisk in parentheses).
If the obsolete -k option is set, all variable assignment arguments are
placed in the environment, even if they occur after the command name. The
following first prints "a=b c" and then c:
echo a=b c
set -k
echo a=b c
This feature is intended for use with scripts written for early versions of
the shell and its use in new scripts is strongly discouraged. It is likely
to disappear someday.
Functions
For historical reasons, there are two ways to define functions, the name()
syntax and the function name syntax, described in the Commands section
above. Shell functions are read in and stored internally. Alias names are
resolved when the function is read. Functions are executed like commands
with the arguments passed as positional parameters. (See Execution below.)
Functions defined by the function name syntax and called by name execute in
the same process as the caller and share all files and present working
directory with the caller. Traps caught by the caller are reset to their
default action inside the function. A trap condition that is not caught or
ignored by the function causes the function to terminate and the condition
to be passed on to the caller. A trap on EXIT set inside a function is
executed after the function completes in the environment of the caller.
Ordinarily, variables are shared between the calling program and the
function. However, the typeset special built-in command used within a
function defines local variables whose scope includes the current function
and all functions it calls. Errors within functions return control to the
caller.
Functions defined with the name() syntax and functions defined with the
function name syntax that are invoked with the . special built-in are
executed in the caller's environment and share all variables and traps with
the caller. Errors within these function executions cause the script that
contains them to abort.
The special built-in command return is used to return from function calls.
Function names can be listed with the -f or +f option of the typeset
special built-in command. The text of functions, when available, will also
be listed with -f. Functions can be undefined with the -f option of the
unset special built-in command.
Ordinarily, functions are unset when the shell executes a shell script.
Functions that need to be defined across separate invocations of the shell
should be placed in a directory and the FPATH variable should contains the
name of this directory. They may also be specified in the ENV file.
Jobs
If the monitor option of the set command is turned on, an interactive shell
associates a job with each pipeline. It keeps a table of current jobs,
printed by the jobs command, and assigns them small integer numbers. When a
job is started asynchronously with &, the shell prints a line which looks
like:
[1] 1234
indicating that the job which was started asynchronously was job number 1
and had one (top-level) process, whose process id was 1234.
This paragraph and the next require features that are not in all versions
of UNIX and may not apply. If you are running a job and wish to do
something else you may hit the key ^Z (control-Z) which sends a STOP signal
to the current job. The shell will then normally indicate that the job has
been `Stopped', and print another prompt. You can then manipulate the state
of this job, putting it in the background with the bg command, or run some
other commands and then eventually bring the job back into the foreground
with the foreground command fg. A ^Z takes effect immediately and is like
an interrupt in that pending output and unread input are discarded when it
is typed.
A job being run in the background will stop if it tries to read from the
terminal. Background jobs are normally allowed to produce output, but this
can be disabled by giving the command "stty tostop". If you set this tty
option, then background jobs will stop when they try to produce output like
they do when they try to read input.
There are several ways to refer to jobs in the shell. A job can be referred
to by the process id of any process of the job or by one of the following:
% number
The job with the given number.
% string
Any job whose command line begins with string.
%? string
Any job whose command line contains string.
%% Current job.
%+ Equivalent to %%.
%- Previous job.
The shell learns immediately whenever a process changes state. It normally
informs you whenever a job becomes blocked so that no further progress is
possible, but only just before it prints a prompt. This is done so that it
does not otherwise disturb your work. The notify option causes the shell to
print these job change messages as soon as they occur.
When the monitor option is on, each background job that completes triggers
any trap set for CHLD.
When you try to leave the shell while jobs are running or stopped, you will
be warned that `You have stopped(running) jobs.' You may use the jobs
command to see what they are. If you immediately try to exit again, the
shell will not warn you a second time, and the stopped jobs will be
terminated. When a login shell receives a HUP signal, it sends a HUP signal
to each job that has not been disowned with the disown built-in command
described below.
Signals
The INT and QUIT signals for an invoked command are ignored if the command
is followed by & and the monitor option is not active. Otherwise, signals
have the values inherited by the shell from its parent (but see also the
trap built-in command below).
Execution
Each time a command is read, the above substitutions are carried out. If
the command name matches one of the Special built-in Commands listed below,
it is executed within the current shell process. Next, the command name is
checked to see if it matches a user defined function. If it does, the
positional parameters are saved and then reset to the arguments of the
function call. When the function completes or issues a return, the
positional parameter list is restored. For functions defined with the
function name syntax, any trap set on EXIT within the function is executed.
The value of a function is the value of the last command executed. A
function is also executed in the current shell process. If a command name
is not a special built-in command or a user defined function, but it is one
of the built-in commands listed below it is executed in the current shell
process.
The shell variable PATH defines the search path for the directory
containing the command. Alternative directory names are separated by a
colon (:). The default path is /bin:/usr/bin: (specifying /bin, /usr/bin,
and the current directory in that order). The current directory can be
specified by two or more adjacent colons, or by a colon at the beginning or
end of the path list. If the command name contains a / then the search path
is not used. Otherwise, each directory in the path is searched for an
executable file that is not a directory. If the shell determines that there
is a built-in version of a command corresponding to a given pathname, this
built-in is invoked in the current process. A process is created and an
attempt is made to execute the command via exec(2). If the file has execute
permission but is not an a.out file, it is assumed to be a file containing
shell commands. A separate shell is spawned to read it. All non-exported
variables are removed in this case. If the shell command file doesn't have
read permission, or if the setuid and/or setgid bits are set on the file,
then the shell executes an agent whose job it is to set up the permissions
and execute the shell with the shell command file passed down as an open
file. A parenthesized command is executed in a sub-shell without removing
non-exported variables.
Command Re-entry
The text of the last HISTSIZE (default 128) commands entered from a
terminal device is saved in a history file. The file $HOME/.sh_history is
used if the HISTFILE variable is not set or if the file it names is not
writable. A shell can access the commands of all interactive shells which
use the same named HISTFILE. The built-in command hist is used to list or
edit a portion of this file. The portion of the file to be edited or listed
can be selected by number or by giving the first character or characters of
the command. A single command or range of commands can be specified. If you
do not specify an editor program as an argument to hist then the value of
the variable HISTEDIT is used. If HISTEDIT is unset, the obsolete variable
FCEDIT is used. If FCEDIT is not defined then /bin/ed is used. The edited
command(s) is printed and re-executed upon leaving the editor unless you
quit without writing. The -s option (an in obsolete versions, the editor
name -) is used to skip the editing phase and to re-execute the command. In
this case a substitution parameter of the form old=new can be used to
modify the command before execution. For example, with the preset alias r,
which is aliased to "'hist-s'" typing `r bad=good c' will re-execute the
most recent command which starts with the letter c, replacing the first
occurrence of the string bad with the string good.
In-line Editing Options
Normally, each command line entered from a terminal device is simply typed
followed by a newline (RETURN or LINE FEED). If either the emacs, gmacs,
or vi option is active, the user can edit the command line. To be in either
of these edit modes set the corresponding option. An editing option is
automatically selected each time the VISUAL or EDITOR variable is assigned
a value ending in either of these option names.
The editing features require that the user's terminal accept RETURN as
carriage return without line feed and that a space (` ') must overwrite the
current character on the screen.
The editing modes implement a concept where the user is looking through a
window at the current line. The window width is the value of COLUMNS if it
is defined, otherwise 80. If the window width is too small to display the
prompt and leave at least 8 columns to enter input, the prompt is truncated
from the left. If the line is longer than the window width minus two, a
mark is displayed at the end of the window to notify the user. As the
cursor moves and reaches the window boundaries the window will be centered
about the cursor. The mark is a >" *) if the line extends on the right
(left, both) side(s) of the window.
The search commands in each edit mode provide access to the history file.
Only strings are matched, not patterns, although a leading ^ in the string
restricts the match to begin at the first character in the line.
Each of the edit modes has an operation to list the files or commands that
match a partially entered word. When applied to the first word on the line,
or the first word after a ;, |, &, or (, and the word does not begin with ~
or contain a /, the list of aliases, functions, and executable commands
defined by the PATH variable that could match the partial word is
displayed. Otherwise, the list of files that match the given word is
displayed. If the partially entered word does not contain any file
expansion characters, a * is appended before generating these lists. After
displaying the generated list, the input line is redrawn. These operations
are called command name listing and file name listing, respectively. There
are additional operations, referred to as command name completion and file
name completion, which compute the list of matching commands or files, but
instead of printing the list, replace the current word with a complete or
partial match. For file name completion, if the match is unique, a / is
appended if the file is a directory and a space is appended if the file is
not a directory. Otherwise, the longest common prefix for all the matching
files replaces the word. For command name completion, only the portion of
the file names after the last / are used to find the longest command
prefix. If only a single name matches this prefix, then the word is
replaced with the command name followed by a space.
Key Bindings
The KEYBD trap can be used to intercept keys as they are typed and change
the characters that are actually seen by the shell. This trap is executed
after each character (or sequence of characters when the first character is
ESC) is entered while reading from a terminal. The variable .sh.edchar
contains the character or character sequence which generated the trap.
Changing the value of .sh.edchar in the trap action causes the shell to
behave as if the new value were entered from the keyboard rather than the
original value.
The variable .sh.edcol is set to the input column number of the cursor at
the time of the input. The variable .sh.edmode is set to ESC when in vi
insert mode (see below) and is null otherwise. By prepending
${.sh.editmode} to a value assigned to .sh.edchar it will cause the shell
to change to control mode if it is not already in this mode.
This trap is not invoked for characters entered as arguments to editing
directives, or while reading input for a character search.
Emacs Editing Mode
This mode is entered by enabling either the emacs or gmacs option. The only
difference between these two modes is the way they handle ^T. To edit, the
user moves the cursor to the point needing correction and then inserts or
deletes characters or words as needed. All the editing commands are control
characters or escape sequences. The notation for control characters is
caret ( ^ ) followed by the character. For example, ^F is the notation for
control F. This is entered by depressing `f' while holding down the `CTRL'
(control) key. The `SHIFT' key is not depressed. (The notation ^? indicates
the DEL (delete) key.)
The notation for escape sequences is M- followed by a character. For
example, M-f (pronounced Meta f) is entered by depressing ESC (ascii 033)
followed by `f'. (M-F would be the notation for ESC followed by `SHIFT'
(capital) `F'.)
All edit commands operate from any place on the line (not just at the
beginning). Neither the RETURN nor the LINE FEED key is entered after edit
commands except when noted.
^F Move cursor forward (right) one character.
M-f Move cursor forward one word. (The emacs editor's idea of a word is a
string of characters consisting of only letters, digits and
underscores.)
^B Move cursor backward (left) one character.
M-b Move cursor backward one word.
^A Move cursor to start of line.
^E Move cursor to end of line.
^] char
Move cursor forward to character char on current line.
M-^] char
Move cursor backward to character char on current line.
^X^X
Interchange the cursor and mark.
erase
(User defined erase character as defined by the stty(1) command,
usually ^H or #.) Delete previous character.
^D Delete current character.
M-d Delete current word.
M-^H
(Meta-backspace) Delete previous word.
M-h Delete previous word.
M-^?
(Meta-DEL) Delete previous word (if your interrupt character is ^?
(DEL, the default) then this command will not work).
^T Transpose current character with next character in emacs mode.
Transpose two previous characters in gmacs mode.
^C Capitalize current character.
M-c Capitalize current word.
M-l Change the current word to lower case.
^K Delete from the cursor to the end of the line. If preceded by a
numerical parameter whose value is less than the current cursor
position, then delete from given position up to the cursor. If preceded
by a numerical parameter whose value is greater than the current cursor
position, then delete from cursor up to given cursor position.
^W Kill from the cursor to the mark.
M-p Push the region from the cursor to the mark on the stack.
kill
(User defined kill character as defined by the stty command, usually ^G
or @.) Kill the entire current line. If two kill characters are entered
in succession, all kill characters from then on cause a line feed
(useful when using paper terminals).
^Y Restore last item removed from line. (Yank item back to the line.)
^L Line feed and print current line.
^@ (Null character) Set mark.
M- space
(Meta space) Set mark.
^J (New line) Execute the current line.
^M (Return) Execute the current line.
eof End-of-file character, normally ^D, is processed as an End-of-file only
if the current line is null.
^P Fetch previous command. Each time ^P is entered the previous command
back in time is accessed. Moves back one line when not on the first
line of a multi-line command.
M-< Fetch the least recent (oldest) history line.
M-> Fetch the most recent (youngest) history line.
^N Fetch next command line. Each time ^N is entered the next command line
forward in time is accessed.
^R string
Reverse search history for a previous command line containing string.
If a parameter of zero is given, the search is forward. String is
terminated by a RETURN or NEW LINE. If string is preceded by a ^, the
matched line must begin with string. If string is omitted, then the
next command line containing the most recent string is accessed. In
this case a parameter of zero reverses the direction of the search.
^O Operate - Execute the current line and fetch the next line relative to
current line from the history file.
M- digits
(Escape) Define numeric parameter, the digits are taken as a parameter
to the next command. The commands that accept a parameter are ^F, ^B,
erase, ^C, ^D, ^K, ^R, ^P, ^N, ^], M-., M-^], M-_, M-b, M-c, M-d, M-f,
M-h, M-l and M-^H.
M- letter
Soft-key - Your alias list is searched for an alias by the name _
letter and if an alias of this name is defined, its value will be
inserted on the input queue. The letter must not be one of the above
meta-functions.
M-[ letter
Soft-key - Your alias list is searched for an alias by the name __
letter and if an alias of this name is defined, its value will be
inserted on the input queue. The can be used to program functions keys
on many terminals.
M-. The last word of the previous command is inserted on the line. If
preceded by a numeric parameter, the value of this parameter determines
which word to insert rather than the last word.
M-_ Same as M-..
M-* Attempt file name generation on the current word. An asterisk is
appended if the word doesn't match any file or contain any special
pattern characters.
Command or file name completion as described above.
M-= Command or file name listing as described above.
^U Multiply parameter of next command by 4.
\ Escape next character. Editing characters, the user's erase, kill and
interrupt (normally ^?) characters may be entered in a command line or
in a search string if preceded by a \. The \ removes the next
character's editing features (if any).
^V Display version of the shell.
M-# If the line does not begin with a #, a # is inserted at the beginning
of the line and after each newline, and the line is entered. This
causes a comment to be inserted in the history file. If the line begins
with a #, the # is deleted and one # after each newline is also
deleted.
Vi Editing Mode
There are two typing modes. Initially, when you enter a command you are in
the input mode. To edit, the user enters control mode by typing ESC (033)
and moves the cursor to the point needing correction and then inserts or
deletes characters or words as needed. Most control commands accept an
optional repeat count prior to the command.
When in vi mode on most systems, canonical processing is initially enabled
and the command will be echoed again if the speed is 1200 baud or greater
and it contains any control characters or less than one second has elapsed
since the prompt was printed. The ESC character terminates canonical
processing for the remainder of the command and the user can then modify
the command line. This scheme has the advantages of canonical processing
with the type-ahead echoing of raw mode.
If the option viraw is also set, the terminal will always have canonical
processing disabled. This mode is implicit for systems that do not support
two alternate end of line delimiters, and may be helpful for certain
terminals.
Input Edit Commands
By default the editor is in input mode.
erase
(User defined erase character as defined by the stty command, usually
^H or #.) Delete previous character.
^W Delete the previous blank separated word. One some systems the viraw
option may be required for this to work.
eof As the first character of the line causes the shell to terminate unless
the ignoreeof option is set. Otherwise this character is ignored.
^V Escape next character. Editing characters and the user's erase or kill
characters may be entered in a command line or in a search string if
preceded by a ^V. The ^V removes the next character's editing features
(if any). One some systems the viraw option may be required for this to
work.
\ Escape the next erase or kill character.
Motion Edit Commands
These commands will move the cursor.
[count]l
Cursor forward (right) one character.
[count]w
Cursor forward one alpha-numeric word.
[count]W
Cursor to the beginning of the next word that follows a blank.
[count]e
Cursor to end of word.
[count]E
Cursor to end of the current blank delimited word.
[count]h
Cursor backward (left) one character.
[count]b
Cursor backward one word.
[count]B
Cursor to preceding blank separated word.
[count]|
Cursor to column count.
[count]fc
Find the next character c in the current line.
[count]Fc
Find the previous character c in the current line.
[count]tc
Equivalent to f followed by h.
[count]Tc
Equivalent to F followed by l.
[count];
Repeats count times, the last single character find command, f, F, t,
or T.
[count],
Reverses the last single character find command count times.
0 Cursor to start of line.
^ Cursor to first non-blank character in line.
$ Cursor to end of line.
% Moves to balancing (, ), {, }, [, or ]. If cursor is not on one of the
above characters, the remainder of the line is searched for the first
occurrence of one of the above characters first.
Search Edit Commands
These commands access your command history.
[count]k
Fetch previous command. Each time k is entered the previous command
back in time is accessed.
[count]-
Equivalent to k.
[count]j
Fetch next command. Each time j is entered the next command forward in
time is accessed.
[count]+
Equivalent to j.
[count]G
The command number count is fetched. The default is the least recent
history command.
/ string
Search backward through history for a previous command containing
string. String is terminated by a RETURN or NEW LINE. If string is
preceded by a ^, the matched line must begin with string. If string is
null the previous string will be used.
? string
Same as / except that search will be in the forward direction.
n Search for next match of the last pattern to / or ? commands.
N Search for next match of the last pattern to / or ?, but in reverse
direction.
Text Modification Edit Commands
These commands will modify the line.
a Enter input mode and enter text after the current character.
A Append text to the end of the line. Equivalent to $a.
[count]cmotion
c[count]motion
Delete current character through the character that motion would move
the cursor to and enter input mode. If motion is c, the entire line
will be deleted and input mode entered.
C Delete the current character through the end of line and enter input
mode. Equivalent to c$.
S Equivalent to cc.
D Delete the current character through the end of line. Equivalent to d$.
[count]dmotion
d[count]motion
Delete current character through the character that motion would move
to. If motion is d, the entire line will be deleted.
i Enter input mode and insert text before the current character.
I Insert text before the beginning of the line. Equivalent to 0i.
[count]P
Place the previous text modification before the cursor.
[count]p
Place the previous text modification after the cursor.
R Enter input mode and replace characters on the screen with characters
you type overlay fashion.
[count]rc
Replace the count character(s) starting at the current cursor position
with c, and advance the cursor.
[count]x
Delete current character.
[count]X
Delete preceding character.
[count].
Repeat the previous text modification command.
[count]~
Invert the case of the count character(s) starting at the current
cursor position and advance the cursor.
[count]_
Causes the count word of the previous command to be appended and input
mode entered. The last word is used if count is omitted.
* Causes an * to be appended to the current word and file name generation
attempted. If no match is found, it rings the bell. Otherwise, the word
is replaced by the matching pattern and input mode is entered.
\ Command or file name completion as described above.
Other Edit Commands
Miscellaneous commands.
[count]ymotion
y[count]motion
Yank current character through character that motion would move the
cursor to and puts them into the delete buffer. The text and cursor are
unchanged.
Y Yanks from current position to end of line. Equivalent to y$.
u Undo the last text modifying command.
U Undo all the text modifying commands performed on the line.
[count]v
Returns the command "hist -e ${VISUAL:-${EDITOR:-vi}}" " count" in the
input buffer. If count is omitted, then the current line is used.
^L Line feed and print current line. Has effect only in control mode.
^J (New line) Execute the current line, regardless of mode.
^M (Return) Execute the current line, regardless of mode.
# If the first character of the command is a #, then this command deletes
this # and each # that follows a newline. Otherwise, sends the line
after inserting a # in front of each line in the command. Useful for
causing the current line to be inserted in the history as a comment and
uncommenting previously commented commands in the history file.
= Command or file name listing as described above.
@ letter
Your alias list is searched for an alias by the name _ letter and if an
alias of this name is defined, its value will be inserted on the input
queue for processing.
Built-in Commands
The following simple-commands are executed in the shell process.
Input/Output redirection is permitted. Unless otherwise indicated, the
output is written on file descriptor 1 and the exit status, when there is
no syntax error, is zero. Except for :, true, false, echo, command, newgrp,
and login, all built-in commands accept -- to indicate end of options. They
also interpret the option -? as a help request and print a usage message on
standard error. Commands that are preceded by one or two asterisks in
parentheses are special built-in commands and are treated specially in the
following ways:
1. Variable assignment lists preceding the command remain in effect when
the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. They are not valid function names.
5. Words, following a command preceded by (**) that are in the format of
a variable assignment, are expanded with the same rules as a variable
assignment. This means that tilde substitution is performed after the
= sign and field splitting and file name generation are not performed.
(*) : [ arg ...]
The command only expands parameters.
(*) . name [ arg ...]
If name is a function defined with the function name reserved word
syntax, the function is executed in the current environment (as if it
had been defined with the name() syntax.) Otherwise if name refers to a
file, the file is read in its entirety and the commands are executed in
the current shell environment. The search path specified by PATH is
used to find the directory containing file. If any arguments arg are
given, they become the positional parameters while processing the .
command and are restored upon completion. Otherwise the positional
parameters are unchanged. The exit status is the exit status of the
last command executed.
(**) alias [ -ptx ] [ name[ =value ] ] ...
The alias command with no arguments prints the list of aliases in the
form name=value on standard output. The -p option causes the word alias
to be inserted before each one. When one or more arguments are given an
alias is defined for each name whose value is given. A trailing space
in value causes the next word to be checked for alias substitution. The
obsolete -t option is used to set and list tracked aliases. The value
of a tracked alias is the full pathname corresponding to the given
name. The value becomes undefined when the value of PATH is reset but
the alias remains tracked. Without the -t option, for each name in the
argument list for which no value is given, the name and value of the
alias is printed. The obsolete -x option has no effect. The exit status
is non-zero if a name is given, but no value, and no alias has been
defined for the name.
bg [ job...]
This command is only on systems that support job control. Puts each
specified job into the background. The current job is put in the
background if job is not specified. See Jobs for a description of the
format of job.
(*) break [ n ]
Exit from the enclosing for, while, until, or select loop, if any. If n
is specified then break n levels.
builtin [ -ds ] [ -f file ] [ name ...]
If name is not specified, the built-ins are printed on standard output.
The -s option prints only the special built-ins. Otherwise, each name
represents the pathname whose basename is the name of the built-in. The
entry point function name is determined by prepending b_ to the built-
in name. Special built-ins cannot be bound to a pathname or deleted.
The -d option deletes each of the given built-ins. On systems that
support dynamic loading, the -f option names a shared library
containing the code for built-ins. Once a library is loaded, its
symbols become available for subsequent invocations of builtin.
Multiple libraries can be specified with separate invocations of the
builtin command. Libraries are searched in the reverse order in which
they are specified.
cd [ -LP ] [ arg ]
cd [ -LP ] old new
This command can be in either of two forms. In the first form it
changes the current directory to arg. If arg is - the directory is
changed to the previous directory. The shell variable HOME is the
default arg. The variable PWD is set to the current directory. The
shell variable CDPATH defines the search path for the directory
containing arg. Alternative directory names are separated by a colon
(:). The default path is <null> (specifying the current directory).
Note that the current directory is specified by a null path name, which
can appear immediately after the equal sign or between the colon
delimiters anywhere else in the path list. If arg begins with a / then
the search path is not used. Otherwise, each directory in the path is
searched for arg.
The obsolete second form of cd substitutes the string new for the string
old in the current directory name, PWD and tries to change to this new
directory.
By default, symbolic links are not followed when finding the directory
name. This is equivalent to the -L option. The -P option causes symbolic
links to be followed when determining the directory. The last instance of
-L or -P determines which method is used.
The cd command may not be executed by rksh. Without the -v or -V options,
command executes name with the arguments given by arg. The -p option causes
a default path to be searched rather than the one defined by the value of
PATH. Functions will not be searched for when finding name. In addition, if
name refers to a special built-in, none of the special properties
associated with the leading daggers will be honored. (For example, the
predefined alias "redirect='command exec'" prevents a script from
terminating when an invalid redirection is given.) With the -v option,
command is equivalent to the built-in whence command described below. The
-V options, causes command to "whence-v"
(*) continue [ n ]
Resume the next iteration of the enclosing for, while, until, or select
loop. If n is specified then resume at the n-th enclosing loop.
disown [ job... ]
Causes the shell not to send a HUP signal to each given job, or all
active jobs if job is omitted, when a login shell terminates.
echo [ arg... ]
When the first arg does not begin with a -, and none of the arguments
contain a \, then echo prints each of its arguments separated by a
space and terminated by a newline. Otherwise, the behavior of echo is
system dependent and print or printf described below should be used.
See echo(1) for usage and description.
(*) eval [ arg ... ]
The arguments are read as input to the shell and the resulting
command(s) executed.
(*) exec [ -c ] [ -a name ] [ arg ... ]
If arg is given, the command specified by the arguments is executed in
place of this shell without creating a new process. The -c option
causes the environment to be cleared before applying variable
assignments associated with the exec invocation. The -a option causes
name rather than the first arg, to become argv[0] for the new process.
Input/output arguments may appear and affect the current process. If
arg is not given the effect of this command is to modify file
descriptors as prescribed by the input/output redirection list. In this
case, any file descriptor numbers greater than 2 that are opened with
this mechanism are closed when invoking another program.
(*) exit [ n ]
Causes the shell to exit with the exit status specified by n. The value
will be the least significant 8 bits of the specified status. If n is
omitted then the exit status is that of the last command executed. An
end-of-file will also cause the shell to exit except for a shell which
has the ignoreeof option (see set below) turned on.
(**) export [ -p ] [ name[=value] ] ...
If name is not given, the names and values of each variable with the
export attribute are printed with the values quoted in a manner that
allows them to be re-inputed. The -p option causes the word export to
be inserted before each one. Otherwise, the given names are marked for
automatic export to the environment of subsequently-executed commands.
fg [ job... ]
This command is only on systems that support job control. Each job
specified is brought to the foreground and waited for in the specified
order. Otherwise, the current job is brought into the foreground. See
Jobs for a description of the format of job.
getconf name [ pathname ]
Prints the current value of the configuration parameter given by name.
getopts optstring vname [ arg ... ]
Checks arg for legal options. If arg is omitted, the positional
parameters are used. An option argument begins with a + or a -. An
option not beginning with + or - or the argument - - ends the options.
optstring contains the letters that getopts recognizes. If a letter is
followed by a :, that option is expected to have an argument. The
options can be separated from the argument by blanks.
The getopts command places the next option letter it finds inside
variable vname each time it is invoked with a + prepended when arg
begins with a +. The index of the next arg is stored in OPTIND. The
option argument, if any, gets stored in OPTARG.
A leading : in optstring causes getopts to store the letter of an
invalid option in OPTARG, and to set vname to ? for an unknown option
and to : when a required option is missing. Otherwise, getopts prints
an error message. The exit status is non-zero when there are no more
options.
There is no way to specify any of the options :, +, -, ?, [, and ]. The
option # can only be specified as the first option.
hist [ -e ename ] [ -nlr ] [ first [ last ] ]
hist -s [ old=new ] [ command ]
In the first form, a range of commands from first to last is selected
from the last HISTSIZE commands that were typed at the terminal. The
arguments first and last may be specified as a number or as a string. A
string is used to locate the most recent command starting with the
given string. A negative number is used as an offset to the current
command number. If the -l option is selected, the commands are listed
on standard output. Otherwise, the editor program ename is invoked on a
file containing these keyboard commands. If ename is not supplied, then
the value of the variable HISTEDIT is used. If HISTEDIT is not set then
FCEDIT (default /bin/ed) is used as the editor. When editing is
complete, the edited command(s) is executed if the changes have been
saved. If last is not specified then it will be set to first. If first
is not specified the default is the previous command for editing and
-16 for listing. The option -r reverses the order of the commands and
the option -n suppresses command numbers when listing. In the second
form the command is re-executed after the substitution old=new is
performed.
jobs [ -lnp ] [ job ... ]
Lists information about each given job; or all active jobs if job is
omitted. The -l option lists process ids in addition to the normal
information. The -n option only displays jobs that have stopped or
exited since last notified. The -p option causes only the process
group to be listed. See Jobs for a description of the format of job.
kill [ -s signame ] job ...
kill [ -n signum ] job ...
kill -l [ sig ... ]
Sends either the TERM (terminate) signal or the specified signal to the
specified jobs or processes. Signals are either given by number with
the -n option or by name with the -s option (as given in <signal.h>,
stripped of the prefix "SIG" with the exception that SIGCLD is named
CHLD). For backward compatibility, the n and s can be omitted and the
number or name placed immediately after the -. If the signal being sent
is TERM (terminate) or HUP (hangup), then the job or process will be
sent a CONT (continue) signal if it is stopped. The argument job can
be the process id of a process that is not a member of one of the
active jobs. See Jobs for a description of the format of job. In the
third form, "kill-l" if sig is not specified, the signal names are
listed. Otherwise, for each sig that is a name, the corresponding
signal number is listed. For each sig that is a number, the signal
name corresponding to the least significant 8 bits of sig is listed.
let arg ...
Each arg is a separate arithmetic expression to be evaluated. See
Arithmetic Evaluation above, for a description of arithmetic expression
evaluation.
The exit status is 0 if the value of the last expression is non-zero,
and 1 otherwise.
(*) newgrp [ arg ... ]
Equivalent to "exec /bin/newgrp" " arg" ....
print [ -Rnprs ] [ -u unit ] [ -f format ] [ arg ... ]
With no options or with option - or - -, each arg is printed on
standard output. The -f option causes the arguments to be printed as
described by printf. In this case any n, r, R options are ignored.
Otherwise, unless the -R or -r, are specified, the following escape
conventions will be applied:
\a The alert character (ascii 07).
\b The backspace character (ascii 010).
\c Causes print to end without processing more arguments and not
adding a newline.
\f The formfeed character (ascii 014).
\n The newline character (ascii 012).
\r The carriage return character (ascii 015).
\t The tab character (ascii 011).
\v The vertical tab character (ascii 013).
\E The escape character (ascii 033).
\\ The backslash character \.
The -R option will print all subsequent arguments and options other
than -n. The -p option causes the arguments to be written onto the
pipe of the process spawned with |& instead of standard output. The
-s option causes the arguments to be written onto the history file
instead of standard output. The -u option can be used to specify a
one digit file descriptor unit number unit on which the output will
be placed. The default is 1. If the option -n is used, no newline
is added to the output.
printf format [ arg ... ]
The arguments arg are printed on standard output in accordance with the
ANSI-C formatting rules associated with the format string format. The
following extensions can also be used:
%b This format can be used instead of %s to cause escape sequences in
the corresponding arg to be expanded as described in print.
%P This format can be used instead of %s to cause arg to be
interpreted as an extended regular expression and be printed as a
shell pattern.
%q This format can be used instead of %s to cause the resulting string
to be quoted in a manner than can be reinput to the shell.
The precision field of the %d format can be followed by a . and the
output base.
pwd [ -LP ]
Outputs the value of the current working directory. If the -P option is
given, all symbolic links are resolved from the name.
read [ -Aprs ]
[ -d delim ]
[ -t timeout ]
[ -u unit] [ vname?prompt ] [ vname ... ]
The shell input mechanism. One line is read and is broken up into
fields using the characters in IFS as separators. The escape
character, \, is used to remove any special meaning for the next
character and for line continuation. The -d option causes the read to
continue to the first character of delim rather than newline. In raw
mode, -r, the \ character is not treated specially. The first field is
assigned to the first vname, the second field to the second vname,
etc., with leftover fields assigned to the last vname. The -A option
causes the variable vname to be unset and each field that is read to be
stored in successive elements of the indexed array vname. The -p option
causes the input line to be taken from the input pipe of a process
spawned by the shell using |&. If the -s option is present, the input
will be saved as a command in the history file. The option -u can be
used to specify a one digit file descriptor unit unit to read from. The
file descriptor can be opened with the exec special built-in command.
The default value of unit n is 0. The option -t is used to specify a
timeout in decimal seconds when reading from a terminal or pipe. If
vname is omitted then REPLY is used as the default vname. An end-of-
file with the -p option causes cleanup for this process so that another
can be spawned. If the first argument contains a ?, the remainder of
this word is used as a prompt on standard error when the shell is
interactive. The exit status is 0 unless an end-of-file is encountered
or read has timed out.
(**) readonly [ -p ] [ vname[=value] ] ...
If vname is not given the names and values of each variable with the
readonly attribute is printed with the values quoted in a manner that
allows them to be re-inputed. The -p option causes the word readonly to
be inserted before each one. Otherwise, the given vnames are marked
readonly and these names cannot be changed by subsequent assignment.
(*) return [ n ]
Causes a shell function or . script to return to the invoking script
with the return status specified by n. The value will be the least
significant 8 bits of the specified status. If n is omitted then the
return status is that of the last command executed. If return is
invoked while not in a function or a . script, then it behaves the same
as exit.
(*) set [ +/-CPabefhkmnopstuvx ] [ +/-o option ]...
[ +/-A vname ] [ arg ... ]
The options for this command have meaning as follows:
-A Array assignment. Unset the variable vname and assign values
sequentially from the list arg. If +A is used, the variable vname
is not unset first.
-C Prevents redirection > from truncating existing files. Files that
are created are opened with the O_EXCL mode. Require >| to truncate
a file when turned on.
-P Causes the cd and pwd built-in commands to default to physical
mode.
-a All subsequent variables that are defined are automatically
exported.
-b Prints job completion messages as soon as a background job changes
state rather than waiting for the next prompt.
-e If a command has a non-zero exit status, execute the ERR trap, if
set, and exit. This mode is disabled while reading profiles.
-f Disables file name generation.
-h Each command becomes a tracked alias when first encountered.
-k (Obsolete). All variable assignment arguments are placed in the
environment for a command, not just those that precede the command
name.
-m Background jobs will run in a separate process group and a line
will print upon completion. The exit status of background jobs is
reported in a completion message. On systems with job control, this
option is turned on automatically for interactive shells.
-n Read commands and check them for syntax errors, but do not execute
them. Ignored for interactive shells.
-o The following argument can be one of the following option names:
allexport
Same as -a.
errexit
Same as -e.
bgnice
All background jobs are run at a lower priority. This is the
default mode.
emacs
Puts you in an emacs style in-line editor for command entry.
gmacs
Puts you in a gmacs style in-line editor for command entry.
ignoreeof
The shell will not exit on end-of-file. The command exit must
be used.
keyword
Same as -k.
markdirs
All directory names resulting from file name generation have a
trailing / appended.
monitor
Same as -m.
noclobber
Same as -C.
noexec
Same as -n.
noglob
Same as -f.
nolog
Do not save function definitions in history file.
notify
Same as -b.
nounset
Same as -u.
physical
Same as -P.
privileged
Same as -p.
verbose
Same as -v.
trackall
Same as -h.
vi Puts you in insert mode of a vi style in-line editor until you
hit escape character 033. This puts you in control mode. A
return sends the line.
viraw
Each character is processed as it is typed in vi mode.
xtrace
Same as -x.
If no option name is supplied then the current option settings
are printed.
-p Disables processing of the $HOME/.profile file and uses the file
/etc/suid_profile instead of the ENV file. This mode is on whenever
the effective uid (gid) is not equal to the real uid (gid). Turning
this off causes the effective uid and gid to be set to the real uid
and gid.
-s Sort the positional parameters lexicographically.
-t (Obsolete). Exit after reading and executing one command.
-u Treat unset parameters as an error when substituting.
-v Print shell input lines as they are read.
-x Print commands and their arguments as they are executed.
-- Do not change any of the options; useful in setting $1 to a value
beginning with -. If no arguments follow this option then the
positional parameters are unset.
As an obsolete feature, if the first arg is - then the -x and -v
options are turned off and the next arg is treated as the first
argument. Using + rather than - causes these options to be turned
off. These options can also be used upon invocation of the shell.
The current set of options may be found in $-. Unless -A is
specified, the remaining arguments are positional parameters and
are assigned, in order, to $1 $2 .... If no arguments are given
then the names and values of all variables are printed on the
standard output.
(*) shift [ n ]
The positional parameters from $n+1 ... are renamed $1 ... , default n
is 1. The parameter n can be any arithmetic expression that evaluates
to a non-negative number less than or equal to $#.
sleep seconds
Suspends execution for the number of decimal seconds or fractions of a
second given by seconds.
(*) trap [ -p ] [ action ] [ sig ] ...
The -p option causes the trap action associated with each trap as
specified by the arguments to be printed with appropriate quoting.
Otherwise, action will be processed as if it were an argument to eval
when the shell receives signal(s) sig. Each sig can be given as a
number or as the name of the signal. Trap commands are executed in
order of signal number. Any attempt to set a trap on a signal that was
ignored on entry to the current shell is ineffective. If action is
omitted and the first sig is a number, or if action is -, then the
trap(s) for each sig are reset to their original values. If action is
the null string then this signal is ignored by the shell and by the
commands it invokes. If sig is ERR then action will be executed
whenever a command has a non-zero exit status. If sig is DEBUG then
action will be executed before each command. If sig is 0 or EXIT and
the trap statement is executed inside the body of a function, then the
command action is executed after the function completes. If sig is 0 or
EXIT for a trap set outside any function then the command action is
executed on exit from the shell. If sig is KEYBD then action will be
executed whenever a key is read while in emacs, gmacs, or vi mode. The
trap command with no arguments prints a list of commands associated
with each signal number.
(**) typeset [ +/-AHflnprtux ] [ +/-EFLRZi[n] ] [ vname[=value ] ] ...
Sets attributes and values for shell variables and functions. When
invoked inside a function, a new instance of the variables vname is
created. The variables' value and type are restored when the function
completes. The following list of attributes may be specified:
-A Declares vname to be an associate array. Subscripts are strings
rather than arithmetic expressions.
-E Declares vname to be a double precision floating point number. If n
is non-zero it defines the number of significant figures that are
used when expanding vname. Otherwise ten significant figures will
be used.
-F Declares vname to be a double precision floating point number. If n
is non-zero it defines the number of places after the decimal point
that are used when expanding vname. Otherwise ten places after the
decimal point will be used.
-H This option provides UNIX to host-name file mapping on non-UNIX
machines.
-L Left justify and remove leading blanks from value. If n is non-zero
it defines the width of the field, otherwise it is determined by
the width of the value of first assignment. When the variable is
assigned to, it is filled on the right with blanks or truncated, if
necessary, to fit into the field. The -R option is turned off.
-R Right justify and fill with leading blanks. If n is non-zero it
defines the width of the field, otherwise it is determined by the
width of the value of first assignment. The field is left filled
with blanks or truncated from the end if the variable is
reassigned. The -L option is turned off.
-Z Right justify and fill with leading zeros if the first non-blank
character is a digit and the -L option has not been set. Remove
leading zeros if the -L option is also set. If n is non-zero it
defines the width of the field, otherwise it is determined by the
width of the value of first assignment.
-f The names refer to function names rather than variable names. No
assignments can be made and the only other valid options are -t, -u
and -x. The option -t turns on execution tracing for this function.
The option -u causes this function to be marked undefined. The
FPATH variable will be searched to find the function definition
when the function is referenced.
-i Declares vname to be represented internally as integer. The right
hand side of an assignment is evaluated as an arithmetic expression
when assigning to an integer. If n is non-zero it defines the
output arithmetic base, otherwise the the output base will be ten.
-l All upper-case characters are converted to lower-case. The upper-
case option, -u is turned off.
-n Declares vname to be a reference to the variable whose name is
defined by the value of variable vname. This is usually used to
reference a variable inside a function whose name has been passed
as an argument.
-r The given vnames are marked readonly and these names cannot be
changed by subsequent assignment.
-t Tags the variables. Tags are user definable and have no special
meaning to the shell.
-u All lower-case characters are converted to upper-case characters.
The lower-case option, -l, is turned off.
-x The given vnames are marked for automatic export to the environment
of subsequently-executed commands. Variables whose names contain a
. can not be exported.
The -i attribute can not be specified along with -R, -L, -Z, or -f.
Using + rather than - causes these options to be turned off. If no
vname arguments are given a list of vnames (and optionally the
values) of the variables is printed. (Using + rather than - keeps
the values from being printed.) The -p option causes typeset
followed by the the option letters to be printed before each name
rather than the names of the options. If any option other than -p
is given, only those variables which have all of the given options
are printed. Otherwise, the vnames and attributes of all variables
are printed.
ulimit [ -HSacdfmnpstv ] [ limit ]
Set or display a resource limit. The available resources limits are
listed below. Many systems do not contain one or more of these limits.
The limit for a specified resource is set when limit is specified. The
value of limit can be a number in the unit specified below with each
resource, or the value unlimited. The -H and -S options specify whether
the hard limit or the soft limit for the given resource is set. A hard
limit cannot be increased once it is set. A soft limit can be
increased up to the value of the hard limit. If neither the H or S
options is specified, the limit applies to both. The current resource
limit is printed when limit is omitted. In this case the soft limit is
printed unless H is specified. When more that one resource is
specified, then the limit name and unit is printed before the value.
-a Lists all of the current resource limits.
-c The number of 512-byte blocks on the size of core dumps.
-d The number of K-bytes on the size of the data area.
-f The number of 512-byte blocks on files that can be written the
current process or by child processes (files of any size may be
read).
-m The number of K-bytes on the size of physical memory.
-n The number of file descriptors plus 1.
-p The number of 512-byte blocks for pipe buffering.
-s The number of K-bytes on the size of the stack area.
-t The number of seconds to be used by each process.
-v The number of K-bytes for virtual memory.
If no option is given, -f is assumed.
umask [ -S ] [ mask ]
The user file-creation mask is set to mask (see umask(2)). mask can
either be an octal number or a symbolic value as described in chmod(1).
If a symbolic value is given, the new umask value is the complement of
the result of applying mask to the complement of the previous umask
value. If mask is omitted, the current value of the mask is printed.
The -S option causes the mode to be printed as a symbolic value.
Otherwise, the mask is printed in octal.
(*) unalias [ -a ] name ...
The aliases given by the list of names are removed from the alias list.
The -a option causes all the aliases to be unset.
(*)unset [ -fv ] vname ...
The variables given by the list of vnames are unassigned, i.e., their
values and attributes are erased. Readonly variables cannot be unset.
If the -f option is set, then the names refer to function names. If the
-v option is set, then the names refer to variable names. The default
is equivalent to -v. Unsetting ERRNO, LINENO, MAILCHECK, OPTARG,
OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their special meaning
even if they are subsequently assigned to.
wait [ job ... ]
Wait for the specified job and report its termination status. If job is
not given then all currently active child processes are waited for. The
exit status from this command is that of the last process waited for.
See Jobs for a description of the format of job.
whence [ -apv ] name ...
For each name, indicate how it would be interpreted if used as a
command name.
The -v option produces a more verbose report.
The -p option does a path search for name even if name is an alias, a
function, or a reserved word. The -a is similar to the -v option but
causes all interpretations of the given name to be reported.
Invocation
If the shell is invoked by exec(2), and the first character of argument
zero ($0) is -, then the shell is assumed to be a login shell and commands
are read from /etc/profile and then from either .profile in the current
directory or $HOME/.profile, if either file exists. Next, commands are read
from the file named by performing parameter expansion, command
substitution, and arithmetic substitution on the value of the environment
variable ENV if the file exists. If the -s option is not present and arg
is, then a path search is performed on the first arg to determine the name
of the script to execute. The script arg must have read permission and any
setuid and getgid settings will be ignored. If the script is not found on
the path, arg is processed as if it named a built-in command or function.
Commands are then read as described below; the following option are
interpreted by the shell when it is invoked:
-c If the -c option is present then commands are read from the first arg.
Any remaining arguments become position parameters starting at 0.
-s If the -s option is present or if no arguments remain then commands are
read from the standard input. Shell output, except for the output of
the Special Commands listed above, is written to file descriptor 2.
-i If the -i option is present or if the shell input and output are
attached to a terminal (as told by ioctl(2)) then this shell is
interactive. In this case TERM is ignored (so that kill 0 does not kill
an interactive shell) and INTR is caught and ignored (so that wait is
interruptible). In all cases, QUIT is ignored by the shell.
-r If the -r option is present the shell is a restricted shell.
The -I filename option is used to generate a cross reference database that
can be used by a separate utility to find definitions and references for
variables and commands.
The remaining options and arguments are described under the set command
above. An optional - as the first argument is ignored.
rksh only
The rksh command is used to set up login names and execution environments
whose capabilities are more controlled than those of the standard shell.
The actions of rksh are identical to those of ksh, except that the
following are disallowed:
changing directory (see cd(1))
setting or unsetting the value or attributes of SHELL, ENV, or PATH
specifying path or command names containing /
redirecting output (>, >|, <>, and >>)
The restrictions above are enforced after .profile and the ENV files are
interpreted.
When a command to be executed is found to be a shell procedure, rksh
invokes ksh to execute it. Thus, it is possible to provide to the end-user
shell procedures that have access to the full power of the standard shell,
while imposing a limited menu of commands; this scheme assumes that the
end-user does not have write and execute permissions in the same directory.
The net effect of these rules is that the writer of the .profile has
complete control over user actions, by performing guaranteed setup actions
and leaving the user in an appropriate directory (probably not the login
directory).
The system administrator often sets up a directory of commands (i.e.,
/usr/rbin) that can be safely invoked by rksh.
EXIT STATUS
Errors detected by the shell, such as syntax errors, cause the shell to
return a non-zero exit status. Otherwise, the shell returns the exit status
of the last command executed (see also the exit command above). If the
shell is being used non-interactively then execution of the shell file is
abandoned. Run time errors detected by the shell are reported by printing
the command or function name and the error condition. If the line number
that the error occurred on is greater than one, then the line number is
also printed in square brackets ("[]") after the command or function name.
CAVEATS
If a command is executed, and then a command with the same name is
installed in a directory in the search path before the directory where the
original command was found, the shell will continue to exec the original
command. Use the -t option of the alias command to correct this situation.
Some very old shell scripts contain a ^ as a synonym for the pipe character
|.
Using the hist built-in command within a compound command will cause the
whole command to disappear from the history file.
The built-in command . file reads the whole file before any commands are
executed. Therefore, alias and unalias commands in the file will not apply
to any commands defined in the file.
Traps are not processed while a job is waiting for a foreground process.
Thus, a trap on CHLD won't be executed until the foreground job terminates.
FILES
/etc/passwd
/etc/profile
/etc/suid_profile
$HOME/.profile
/tmp/sh*
/dev/null
SEE ALSO
Commands: cat(1), cd(1), chmod(1), cut(1), dtksh(1), echo(1), emacs(1),
env(1), newgrp(1), paste(1), stty(1), test(1), vi(1)
System Calls: dup(2), environ(2), exec(2), fork(2), ioctl(2), lseek(2),
pipe(2), umask(2), wait(2)
Library Functions: rand(3), ulimit(3)
File Formats: a.out(4)
The KornShell, Morris I. Bolsky and David G. Korn, Prentice Hall, 1989,
ISBN 0-13-516972-0.
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